Asthma and COPD Flashcards
Summarize the pathophysiological mechanisms in asthma
Reversible airflow obstruction due to constriction of smooth muscle in the airways
Bronchial wall inflammation leading to mucus hypersecretion and plugging
List common acute asthma precipitants
Viral infection Allergen (dust/pets/pollution/cigarette smoke) Exercise Emotional stress Cold temperature Night time
Define airflow obstruction in the small airways
Airflow obstruction is defined as a FEV1/FVC (measured with spirometry) of <70 %.
What constitutes ‘reversibility’ in bronchodilator response tests for asthma
Post-bronchodilator (10 mins) FEV1 increases more than 200 mL and the increase is greater than 12%.
Classify asthma severity based on % predicted PEFR
Life threatening asthma <33 %
Acute severe asthma 33-50 %
Moderate asthma >50-75 %
Mild asthma >75 %
Define ‘control’ of asthma
No day time symptoms No night time awakening due to asthma No exacerbations No need for rescue treatment No limitations to activity
There may have to be compromise between side effects of treatment and control of symptoms
Describe the step-wise approach to asthma management
Step 1: Salbutamol
Step 2: Salbutamol + Budesonide
Step 3: Salbutamol + Budesonide + Salmeterol (or increased dose of steroid inhaler)
Step 4: As step 3 but trial of high dose inhaled steroid. Consider 4th drug e.g. leukotriene receptor antagonist
Step 5: As step 4 but regular oral steroids at lowest possible dose. Specialist care required
List three different types of inhalers
pressurized meter dose inhaler (pmdi),
breath activated inhalers
dry powder inhalers
How do spacers improve drug delivery
Remove the need for coordination between activation and inhalation
Reduce the velocity of aerosol and subsequent impaction on oropharynx.
What particle size of nebulized solution is appropriate for the treatment of asthma
A drug particle size of 1-5 microns
Should NSAIDS be excluded in all asthmatics
Only 10 % of asthmatics get bronchoconstriction secondary to NSAIDs, therefore it is unnecessary to exclude this useful group of analgesics in all asthmatics.
What are the criteria that define severe asthma
Severe asthma consists of one or more of the following:
Previous near fatal asthma e.g. requiring ventilation
Previous admission for asthma within the previous year
Requires >3 classes of asthma medication
Heavy use of beta-2 agonist
Repeated attendances at A&E
Which commonly used anaesthetic drugs cause histamine release
Morphine (give it slowly
SUX
Thiopental
Mivacurium
Avoid in brittle asthmatics
What is the appearance of the capnograph tracing in asthmatics and why
Up-sloping of the plateau (shark fin like) –> indicates alveoli emptying at different rates.
The expiratory time might need to be prolonged in asthmatics –> what impact does this have on other ventilatory parameters
Decreased inspiratory time –> increased inspiratory pressures
Summarize an approach to laryngospasm, bronchospasm, poor ventilatory effort and pneumothorax
LARYNGOSPASM
Dx - RDS/Stridor/tug/accessory muscles/paradoxical breathing
Rx - Jaw thrust 100% O2 –> CPAP –> Re-intubation
BRONCHOSPASM
Dx - Expiratory wheeze and prolonged expiration
Rx - FiO2 1.0 and BDs
POOR VENTILATORY EFFORT
Dx - Residual sedation/opioids/incomplete recovery from NMB
Rx - BVM with FiO2 1.0 may need re-intubation
(re-sedate in the instance of residual NMB)
PNEUMOTHORAX
Rx - ICD
How is intra-operative bronchospasm diagnosed
Increased airway pressures with difficulty ventilating and upsloping of the capnograph trace ± desaturation
Expiratory wheeze on auscultation
How is intraoperative bronschospasm managed
IMMEDIATE
FiO2 1.0 and call for help
Exclude circuit malfunction/obstruction
Increase [volatile]
High Paw may be needed with I:E 1:4
Consider disconnection to relieve accumulation of autoPEEP
Change LMA to ETT if high pressures required (Aintree fibre-optic).
Drugs:
- B2 agonist puffed into circuit via adaptor or 2.5 - 5 mg salbutamol nebulized into circuit
- If equipment not available: Salbutamol 0.25 mg IV slow IV bolus
SHORT TERM Aminophylline: 5mg/kg IV over 20 mins (If on regular aminophylline: 0.5mg/kg/hr) Hydrocortisone: 100mg IV Magnesium Sulfate: 2 g in 200 ml over 20 mins Adrenalin 10ug boluses IV Ketamine 2mg/kg IV ABG/CXR
DEFINITIVE
If refractory use IV infusion –> ICU
Define COPD
Chronic obstructive pulmonary disease is characterized by a progressive development of airflow limitation that is not fully reversible. Clinically, it encompasses:
Chronic bronchitis
Emphysema
Mucous plugging
What is chronic bronchitis
Presence of productive cough for >3 months for >2 consecutive years.
What is chronic bronchitis
Enlargement of air spaces, destruction of lung parenchyma, loss of lung elasticity and closure of small airways.
What is mucous plugging
Due to bronchial hypersecretion, tenacious secretions and ciliary dysfunction.
List the risk factors for the development of COPD
- Cigarette smoking
- Climate and air pollution
- Occupational exposure: Grain/coal/mineral dust/welding fumes
- Alpha 1 - antitrypsin deficiency
What differences are there between asthma and COPD?
Entity - COPD - Asthma Age - > 35 - Any age Cough - Persistent + Productive - Intermittent and dry Smoking - Almost invariable - Possible Breathlessness - Progressive and persistent - Intermittent and variable Nocturnal Sx - Uncommon - Common Family Hx - Uncommon - common Atopy - Possible - common
What is the purpose of prn reliever inhalers in COPD
Improve exercise tolerance and relieve dyspnoea
When are long acting beta agonists indicated in COPD
If patients remain symptomatic despite prn reliever inhalers a long acting inhaled beta agonist or anticholinergic is added
Describe two different methods of inhaler delivery
Metered-dose inhaler (usually with spacer)
Breath-activated inhaler
What and when are oral medications prescribed
Oral steroids used for acute exacerbations
Severe uncontrolled COPD might warrant maintenance steroids
Oral theophylline is used for more severe COPD
Mucolytics in chronic bronchitis
When are home nebulizers prescribed
For patients with disabling breathlessness and whose disease is uncontrolled on inhalers
What are the benefits of home oxygen
- Improve survival
- Reduce incidence of polycythaemia
- Reduce progression of pulmonary hypertension
- Improve neuropsychological health
How is home oxygen prescribed
Continuous therapy with O2 concentrator > 15 hours/day
Intermittent therapy for short bursts using O2 cylinders
Who is prescribed home O2 therapy
Marked breathlessness at rest with PaO2 < 7.3 kPa
List the non-pharmacological management of patient’s with COPD
- Smoking cessation
- Pulmonary rehabilitation
- exercise
- nutritional - Immunization - Pneumococcus and influenza
- Surgery - bullectomy and lung volume reduction surgery in patients with emphysema
List the benefits of smoking cessation
- Improvement of oxygen carrying capacity due to decrease in COHb (12 - 18 hours)
- Return to normal hepatic enzyme function (6 - 8 weeks)
- Return to normal immune function (6 - 8 weeks)
- Improvement of ciliary and airway function and decreased sputum production
What should be considered in the perioperative period if the patient is on maintenance steroid therapy (>10mg daily)
Perioperative steroid replacement - IV hydrocortisone
Ensure usual prednisone is taken and that regular dosing in the postoperative period
What surgical factors might increase the risk of pulmonary complications
- The closer the incision is to the diaphragm –> hypoventilation and pulmonary complications
(greatest risk for thoracic and upper abdominal surgery) - Postoperative pulmonary complications are lower for laparoscopic versus open surgery
- Increased risk with increased surgical durations
What are the advantages of regional anaesthesia in COPD
Allows maintenance of spontaneous ventilation without irritation of airway
Opioid sparing effect
May facilitate early mobilization
What are the disadvantages of regional anaesthesia in COPD
Patient preference:
- Can patient lie flat and still for duration of surgery
Is sedation required to facilitate regional technique –> respiratory depression
Neuraxial blocks - Sensory level of T6 may compromise intercostal muscle function: reduce coughing efficacy
Pneumothorax risk with supraclavicular approaches to the brachial plexus and interscalene approach to the phrenic nerve
What are the advantages of GA in COPD
- Control of ventilation and ETCO2
- May be necessary for certain types of surgery
- ETT - definitive airway and allows for suction of secretions
- May be required to maintain oxygenation in the face of respiratory depression
What are the disadvantages of GA in COPD
Changes in functional lung volumes –> compromise postoperative resp function in patients with reduced respiratory reserve
Bronchospasm risk from airway instrumentation and histamine releasing drugs
Risk of barotrauma and pneumothorax from IPPV/PEEP/Air trapping
Need to avoid N2O in bullous emphysema due to the risk of rupturing a bullae
Why is vascular access a challenge in patients on long term steroids
Fragile skin and vessel walls
How should drug choices be guided in COPD
Avoid drugs that cause histamine release Morphine Mivacurium SUX Thiopental
How are important lung capacities affected by anaesthesia and surgery
Vital capacity and functional residual capacity are reduced subsequent to the effects of anaesthetic drugs, neuromuscular blocking agents and surgical trauma
What measures are available to help preserve respiratory function and oxygentation
Lung expansion manoeuvres (teach prior to surgery)
- sitting
- deep breathing
- Incentive spirometry (inhalation)
- positive pressure breathing techniques (exhalation)
Chest physiotherapy
Humidified Oxygen therapy, CPAP, nebs, analgesia/RA, (coughing and deep breathing)
How is the need for perioperative steroid replacement assessed
Depends on the dose of long term steroids (>10 mg prednisolone)
Depends on whether surgery is minor, intermediate or major
Can histamine antagonists reduce the effects of histamine releasing drugs in patients with COPD
NO
